Abstract

A vital part of a forensic science investigation is the recovery of DNA from a crime scene.Body fluids such as blood or saliva are most commonly left at the scene of a crime and arefrequently found in only minute quantities. In order to protect the recovery of this criticalevidence it is required to be packaged in such a way that further degradation of the sampleis not a possibility. In the United Kingdom, DNA evidence is packaged in plastic whereasother countries package DNA evidence in paper. This difference is due to the belief that DNAcan degrade in plastic packaging. Evidence of a documented study that proves or disprovesthis theory has not been determined so therefore a study was carried out in order toestablish which packaging would provide the most suitable option for DNA evidence. Thisstudy investigated different drying times prior to saliva samples being stored in either paperor plastic packaging and then determining the DNA quantities present over a set period oftime using quantitative real-time PCR. The results indicated that if a wet saliva sample wasto be immediately placed in plastic packaging and analysed within one week then this wouldprovide the largest concentration of DNA. If this sample was to be analysed eight weeksafter collection, the sample concentration would reduce when compared with a samplepackaged immediately in paper packaging. Even with this reduction the sample immediatelypackaged in plastic presented a consistently higher DNA concentration when compared withall of the other samples. It was determined that if the wet saliva sample was allowed to dryfor six hours and then packaged in plastic packaging, this presents the lowest degree of DNAloss.